This invention relates to rapidly peptizable stabilizing agents comprising microcrystalline cellulose and iota carrageenan. More particularly it relates to stabilizing agents comprising these two components which may be readily peptized in aqueous systems in the presence of other ingredients using minimal agitation.
Attempts have been made in the past to develop improved microcrystalline cellulose-based stabilizing agents for use in dry mix applications such as instant cocoa milk drinks and low fat or fat-free sauces and gravies. These stabilizing agents may perform one or more desired functions depending on the structure of the agent and on its application. Such functions may include gelling, thickening, suspending, texturizing and/or improving mouthfeel. A requirement of these stabilizing agents is that they can be dispersed with minimal agitation, for example, by being stirred in an aqueous environment with a spoon or a wire whisk. As the dry stabilizing agent is dispersed in water, it must also be peptized to obtain functionality. Peptization means that the dry agent is dispersed in water in a colloidal state. Peptization of a dry agent in aqueous media allows the functionality of the agent to be restored to a level near or at the level observed before the agent was dried. Rapidly-peptized drying agents can be dispersed in a colloidal state with minimal agitation. There is a continuing need for rapidly peptized stabilizing agents that provide desired functionality at low use levels in a variety of food and other applications.
In order to prevent hydrogen bonding, Durand et. al. in U.S. Pat. No 3,539,365 suggest coating the attrited microcrystals with a barrier material. Several materials are mentioned for this purpose, but the most effective is stated to be sodium carboxymethylcellulose (CMC). The patent states (at column 5) that methylcellulose, hydroxypropyl methylcellulose, guar gum, alginates, sugars, surfactants, and other hydrocolloids may have a slight barrier action when added in appreciably higher proportions than CMC. Although the use of CMC is very successful as a barrier coating, it is not universally accepted as a food ingredient because it is a chemically modified cellulose derivative rather than a natural ingredient.
Recognizing the unacceptability of CMC in food ingredients in certain well-populated countries, McGinley in U.S. Pat. No. 4,263,334 avoids the use of CMC by teaching a combination of additives consisting of a first ingredient which is a carbohydrate sweetener, e.g., sucrose, dextrose, or hydrolyzed cereal solids, and a second ingredient which is a hydrocolloid, e.g., guar gum, locust bean gum, gum arabic, sodium alginate, propylene glycol alginate, carrageenan, gum karaya, or xanthan gum. There is no teaching of ready dispersibility for this combination which is used as a component of frozen dairy products, e.g., ice cream, to impart desirable organoleptic characteristics to the food.
In an attempt to prepare an easily dispersible stabilizing agent for dry mix food products, in U.S. Pat. No. 4,311,717 McGinley discloses a stabilizing agent which consists of a spray-dried combination of MCC, CMC, and whey or milk solids. Provided this composition is dry blended with certain other food ingredients, it may be dispersed and peptized with minimal agitation. However, when used in a hot drink, the stabilizer tends to float and become lumpy when stirring is initiated. Furthermore, to obtain functionality similar to other colloidal products, it is necessary to use high levels of the material of this invention because more than 50%, often as much as 75%, of the combination is comprised of CMC and whey or milk solids. The presence of CMC precludes the characterization of this stabilizing agent as being xe2x80x9call naturalxe2x80x9d.
An improved stabilizing agent comprising MCC coprocessed with CMC, starch, preferably having a low amylose content, and a diluent, maltodextrin, whey, or non-fat dry milk solids, preferably maltodextrin, is disclosed by Tuason et al. in U.S. Pat. No. 4,980,193. This three-component powder when dry blended with whey and cocoa powder disperses with instant peptization to form a stable cocoa suspension. Stable cocoa suspensions described in the patent required 2.0-3.3% of the stabilizing agent. Like the product of U.S. Pat, No, 4,311,717, the claim of being xe2x80x9call naturalxe2x80x9d cannot be made for this material. Furthermore, manufacture of this three-component stabilizing agent is complex and requires special procedures.
Another MCC-based stabilizing agent is described by Tuason et al. in U.S. Pat. No. 5,366,742. This agent is prepared by mixing colloidal MCC with sodium alginate in water and then adding a soluble calcium salt to the slurry in an amount which deposits a sodium, calcium alginate complex on the surface of the MCC to provide barrier coating properties. After homogenization, the slurry is spray dried. The resulting stabilizing agent may be redispersed in water by use of high shear methods which appear to break the calcium alginate crosslinks, thus allowing dispersion to occur. However, in order to disperse this stabilizing agent using minimal agitation, it is necessary to provide a calcium sequestrant to preferentially react with the calcium in the sodium, calcium complex, thereby solubilizing the alginate.
Few, if any, natural hydrocolloids when coprocessed with MCC provide effective barrier coating properties to the spray-dried powder that is produced. In U.S. Pat. No. 5,192,569 McGinley et al. describe the coprocessing of MCC and a galactomannan gum, e.g., locust bean or guar gum. Prior to spray drying, the MCC is attrited and is, therefore, colloidal. However, the product is claimed to be comprised of spherical particles ranging in size from 0.1 to 100 microns. In Example 1 for instance, spray dried powder has a particle size range of 5-70 microns. Dispersion of this coprocessed material requires high shear conditions. In compositions having 15 weight % or more of the galactomannan gum, high shear dispersion of the spray-dried material results in fibrous particles. Both the dispersed spray-dried granules and the fibrous material are described as being particularly effective in providing fat-like properties to food stuffs.
In contrast to the above materials, the compositions of this invention in which attrited MCC and iota carrageenan are coprocessed in ratios of 80:20 to 50:50, respectively, are readily dispersed and peptized with minimal agitation, e.g., stirring with a spoon or a wire whisk, when they are incorporated in dry mixes. Further, they are capable of stabilization of drinks or salad dressings prepared from these mixes at reduced levels of stabilizer. In addition, since there is no CMC present in these compositions, they may be claimed to be xe2x80x9call naturalxe2x80x9d, and are therefore acceptable in countries where CMC is not acceptable.
It has been found that attrited microcrystalline cellulose and iota carrageenan can be coprocessed at ratios between 80:20 and 50:50, respectively, in an aqueous slurry at or above the temperature at which the iota carrageenan is soluble in water. Spray drying this slurry, for example, produces a dry powder which in a dry mix disperses and peptizes in water with minimal agitation, stabilizing the aqueous drink or sauce prepared from the dry mix. Hereafter in this specification, the word xe2x80x98carrageenanxe2x80x99 is to be construed as meaning iota carrageenan unless a different meaning is clearly indicated. In a second aspect of this invention the stabilizer can be used at significantly lower levels than prior art compositions, including MCC/CMC compositions, to provide stabilization of aqueous foods. Not only is this dispersion and stabilization effective at approximately neutral pH, but it also is effective at strongly acidic pH values, e.g., in vinegar. In addition, it is effective in solutions containing as much as 24 weight percent salt without the requirement for a protective colloid, e.g., xanthan gum, to be present.
In another aspect of this invention there is provided a process to prepare the coprocessed compositions of this invention by first attriting hydrolyzed cellulose wetcake, dispersing the attrited wetcake in water heated to above the temperature at which the particular grade of iota carrageenan being used dissolves, adding the dry carrageenan to the dispersion of microcrystalline cellulose, mixing the components, homogenizing the mixture to assure intimate mixing, and drying the dispersion.
Although not intending to be bound to any particular explanation of the functionality of the compositions of this invention, it has been clearly shown in experiments that the carrageenan provides significant functionality to the composition. Unlike galactomannan gum coprocessed with MCC described in U.S. Pat. No 5,192,569, which does not provide any barrier coating properties at levels up to 30 weight % galactomannan gum, carrageenan provides barrier coating properties at levels as low as 20 weight % of the composition. A second contribution derives its functionality from the close association of the MCC and the carrageenan. In the absence of other viscosifiers, the viscosity of dispersions of this composition is temperature dependent, increasing viscosity occurring as the food cools to an acceptable temperature for ingestion. For example, a gravy prepared with an MCC/carrageenan stabilizer increases in viscosity as it cools, and it may be reheated without modification to provide a smooth gravy having the same viscosity as it had during cooling. In contrast, a starch-based gravy gels as it cools and requires the addition of some starch and water to restore its texture and viscosity upon reheating. This improvement is believed to be attributable to the MCC component of the MCC/carrageenan stabilizer.
The microcrystalline cellulose employed in preparing the compositions of this invention is hydrolyzed cellulose wetcake which has been attrited to provide colloidal particles of MCC. For purposes of this invention colloidal is intended to mean having a particle size in the range of 0.1 xcexcm to 10 xcexcm in which at least 60% of the particles have a particle size of 0.2 xcexcm or less. It is necessary for this attrition step to be done in the absence of iota carrageenan because this type of carrageenan interferes with the attrition by reducing the abrasion between cellulose particles required to release the cellulose crystallites.
Iota carrageenan, a polysaccharide which is comprised of repeating galactose units and 3,6-anhydrogalactose units is suitable for the compositions of this invention. A rich source of iota carrageenan is the seaweed Euchema spinosum. The approximate content of anhydrogalactose units in iota carrageenan is 30% whereas kappa carrageenan has 34% anhydrogalactose units and lambda carrageenan is essentially devoid of these units. Carrageenans are also characterized by the amount of ester sulfate groups that are present on both the galactose and anhydrogalactose units. The ester sulfate content of iota carrageenan may range from about 25% to 34%, preferably about 32%, which is intermediate between kappa carrageenan which has a 25% and lambda carrageenan which has a 35% ester sulfate content. The sodium salt of iota carrageenan is soluble in water, but different grades of iota carrageenan require heating the water to different temperatures to dissolve them. The iota carrageenans which are suitable for this invention are soluble in water heated up to 80xc2x0 C. (176xc2x0 F.). Preferred grades of iota carrageenans are soluble at lower temperatures, for example, at 50xc2x0 C. (122xc2x0 F.).
The useful ratios of attrited MCC to iota carrageenan range from about 80:20 to 50:50, respectively. To have adequate carrageenan present for barrier coating properties, the minimum level of carrageenan must be at least about 20 weight %. A preferred. composition, about 70 weight % MCC and 30 weight % iota carrageenan, is suitable for general purpose use in a wide variety of applications. However, the 50:50 composition has properties which make it particularly suitable for use in milk-based applications, especially when some gelling is desirable.
The process to prepare the compositions of this invention begins with the attrition of hydrolyzed cellulose wetcake. As described above, the hydrolyzed cellulose wetcake is usually produced by the acid hydrolysis of wood pulp to partially depolymerize the cellulose, cleaving the cellulose chains in the amorphous regions, but leaving crystalline portions, called crystallites, hydrogen bonded to each other. The attrition is a mechanical step in which the partially depolymerized cellulose is placed under high shear in a variety of environments, e.g., Waring blenders, ball mills, planetary mixers, or other appropriate mechanical means. During the attrition process, the cellulose particles rub against each other, and the ensuing friction causes the individual crystallites to be separated or xe2x80x9cpeeledxe2x80x9d from the fiber or fragment, freeing the crystallites. After attrition, the colloidal cellulose is dispersed in an appropriate amount of water that has been heated to a temperature at or above the dissolution temperature of the iota carrageenan with which it is to be coprocessed. For example, a satisfactory temperature of the cellulose dispersion would be approximately 57xc2x0 C. when an iota carrageenan having an aqueous dissolution temperature of 50xc2x0 C. is being used. The dry carrageenan is then added to the cellulose dispersion with agitation to dissolve the carrageenan. After the carrageenan has been completely dissolved, the dispersion is homogenized to assure intimate mixing of the MCC and carrageenan. The homogenized dispersion is then dried in a manner which produces a readily reconstitutable powder.
The method of drying, i.e., removing the water from the dispersion, may be any method which ultimately produces a reconstitutable powder. One such method is spray drying, a method which is frequently used to produce microcrystalline cellulose and microcrystalline cellulose coprocessed with, for example, carboxymethylcellulose or galactomannans. An alternative to spray drying involves the following steps. First, one or two volumes of alcohol, e.g., 75% aqueous isopropanol, is added to each volume of dispersion. This causes the solids in the dispersion to flocculate. These solids may be filtered, dried, and milled to a powder having the same properties as spray-dried powder.
When incorporated into dry food mixes, e.g., instant cocoa drinks, instant soups, gravies, salad dressings, puddings and the like, the stabilizing agents of this invention may easily be dispersed and peptized by simply stirring the mix in water with a spoon or a wire whisk. These stabilizing agents have a unique combination of properties, including low pH stability, milk gelling properties, stability in high concentrations of salt, and freeze/thaw stability in frozen desserts. These are properties not previously provided by a single microcrystalline cellulose-based stabilizing agent. For example, the materials described in U.S. Pat. No. 5,366,742 (Avicel(copyright) AC) have ready dispersibility provided there is a sequestrant present to counteract the effect of the calcium ions. Also these MCC/alginate materials have pH stability above a pH of 3.5; however, below this pH alginic acid is precipitated, causing destabilization.
The level of stabilizing agent in a food may range from about 0.05 weight % to about about 3 weight %, depending on the particular food being stabilized and the ratio of MCC to iota carrageenan in the stabilizing agent being used. A preferred range is from about 0.05 to about 2 weight %. In addition to being able to be used alone in environments in which other stabilizing agents are currently being used, often in combination with other stabilizers such as xanthan gum and starches, the levels of the stabilizing agents of this invention are lower than the levels required for these other stabilizers. In most applications the need for an additional stabilizer is thus avoided by the use of the stabilizers of this invention. For example, in salad dressings, a 2% level of MCC/carrageenan stabilizer can successfully replace 2.5% of an MCC/CMC product (Avicel(copyright) CL-611) which requires 0.4% of xanthan gum to be present as a protective colloid in the acidic and salty environment. In addition to the simplification of using a single stabilizing agent in the salad dressing, there is a manufacturing improvement as well. By using the MCC/carrageenan stabilizing agent, there will no longer be a requirement that equipment be cleaned to remove traces of acid in the system that interfere with the dispersion of an MCC/CMC stabilizer in the next batch of salad dressing.
In a sauce formulation, 2% of the 70:30 MCC/carrageenan stabilizer has been shown to replace 4% of a modified starch, while providing a creamier texture and increased opacity. This sauce also flows more smoothly than the comparative sauce containing 4% of the modified starch. The thickening of this sauce with the MCC/carrageenan occurs as the sauce cools, but, unlike the sauce containing the starch, it maintains its texture and viscosity when the sauce is reheated.
In dry mixes, for example, an instant cocoa mix, only 0.3 weight % of the MCC/carrageenan agent is required to stabilize the suspension of cocoa particles whereas Avicel(copyright) AC is required to be present in 1 weight % for equal stabilization of the cocoa particles.
Dry mixes are comprised of dry components which are dry blended, and at some later time the dry mix is reconstituted in water. The MCC/carrageenan stabilizing agents of this invention in dry mixes are readily reconstituted with minimal agitation (spoon stirring or wire whisk), provided they are mixed with the other components prior to dispersion. This is to be contrasted with wet food systems in which mixing with a greater amount of shear is almost universally used in an aqueous environment. For example, preparation of a salad dressing, a wet food system, comprises dispersing the components of the dressing in water using a Lightnin"" mixer or its equivalent.
In wet foods comprising a significant salt content, dispersion with a Lightnin"" mixer does not require any external heat, provided that the salt is added after the dispersion is prepared. This subsequent addition of salt does not affect the stability of the dispersion. An exception is the dispersion of MCC/carrageenan stabilizers in extremely salty solutions where significant heating is required to disperse them in, for example, soy sauce which contains approximately 24 weight percent salt. Also, in some applications, particularly those involving dispersions in milk, it may be necessary to apply some heat to the mixture to assist in the dispersion. This ready dispersibility is in contrast to the MCC/CMC stabilizing agents, e.g., Avicel(copyright) RC-581, which require high shear dispersion and are sensitive to added salt or acidic conditions.
As previously mentioned, the MCC/iota carrageenan stabilizing agents may be used in rapidly dispersing dry mixes, including instant sauces, gravies, soups, and instant cocoa drinks. They also may be used in such wet food systems as low pH dairy systems including sour cream, yogurt, yogurt drinks, frozen yogurt; baked goods, including pie and pastry fillings; citrus-flavored beverages; salad dressings; and soft-serve and hard pack ice creams with improved creaminess and texture. Other possible uses include cosmetic creams, lotions, toothpaste, paints, polishing agents, and pharmaceutical and pesticide formulations as a suspending aid.